Glycosyltransferases are responsible for synthesis of cell surface glycoproteins and clycolipids. Recently two glycosyltransferases, i.e. an N-acetyl-galactosaminyltransferase which synthesizes blood group A-substance (A-enzyme), and galactosyltransferase, which produces blood group B-substance (B-enzyme), were purified to homogeneity for the first time under the current grant. Establishing the existence of an immunologically crossreactive protein in O-plasma proves that the genes for A-enzyme, B-enzyme, and the O-plasma protein are allelic, and excludes the possibility of the involvement of regulatory control in blood group ABO expression. Human blood contains many other glycosyltransferases which remain to be examined. The objective of the renewal project is to elucidate: 1) genetic and evolutionary relationships of various glycosyltransferases, and 2) genetic mechanism of common (ABO,MN) and rare (A2,Am,Cis AB,Bombay, BM) expression through a biochemical approach. The project consists of the following studies: 1) further structural characterization and detailed kinetic analysis of blood group A- and B- enzymes; 2) development of a method for determination of ABO genotypes by immuno-titration; 3) purification and characterization of N-acetylgalactosaminyltransferase of A2- plasma; 4) study of red cell membrane components related to blood group ABO substances; 5) enzymatic and immunologic characterization of the transferases in plasma with unusual blood types; and 6) purification and characterization of blood group fucosyltransferase and other transferases.